While India may have officially been declared a leprosy-free zone, the disease continues to leave more than 100,000 sufferers often stigmatised and isolated.

Leprosy damages nerve endings and can result in loss of sensation

I met Mamatha at a health clinic in Hyderabad. She was wearing a bright yellow party dress. She is 10-years-old and has leprosy. The doctor asked her to close her eyes and then tickled her face with a nylon bristle.

Mamatha knew this game. Each time she pointed with her finger to the place being tickled. But when a large patch of skin on her left cheek was touched, Mamatha didn't move.

The skin patch is not eczema, which my own 10-year-old daughter suffers from, but leprosy. The disease causes nerve damage and creates what's called "anaesthetic skin".

Now, if you cannot detect heat, cold, or pain you run the risk of serious limb damage. Repeated injury can mean people with leprosy lose fingers and toes.

The clinic is run by the charity LEPRA. The doctor told me that fortunately Mamatha's leprosy had been caught early. A six-month course of antibiotics will cure her.

For the first few weeks I kept crying - and asking why me?

Laxmi, Leprosy sufferer

Her father confided that no-one else in the family knew about Mamatha's illness. He had not even told his wife.

Leprosy is an ancient, much feared disease. But although it is infectious and spread like tuberculosis, it is very hard to catch. Most of us have a natural immunity to the germ responsible.

As soon as patients begin treatment, they cannot pass on the disease. But even though it has been curable for decades leprosy still carries huge stigma and the risk of discrimination. Mamatha's father simply wanted to protect his child from being labelled a leper.

Bold statement

In the past 20 years, 15 million people worldwide have been cured of leprosy - the majority in India.

Recently India announced it had "eliminated" leprosy. That is a pretty bold statement. If something is eliminated you might expect it not to be there any more.

Mohammadi's immune system was damaged before she was cured

But, according to a target set by the World Health Organization, elimination simply means there is now fewer than one case in every 10,000 people. Given India's vast population, this means there are more than a 150,000 new cases each year - 150,000 people each with their own story of leprosy.

Another patient at the clinic, Mahammadi, invited me to her home. She had been cured of leprosy, but the disease damaged her immune system.

She has infected lesions on her arms. Mahammadi showed me the drug she was taking - called thalidomide - the most infamous medicine of the 20th century. It caused birth defects when taken by pregnant women, but is now a specialist treatment for leprosy.

Mahammadi said the name "thalidomide" meant nothing to her, but yes, the clinic had told her it was vital she did not get pregnant during the treatment. Mahammadi's parents said they were praying that the marks left by leprosy would clear from their daughter's arms; otherwise it might be hard for her to find a husband.

Leper colonies

The risk of social rejection is so great that many people cured of leprosy end up living in isolated settlements.

Today there are still more than 1,000 leprosy colonies in India. At the Shantinugar colony outside Hyderabad I came across Laxmi.

She was sitting in the shade bathing her feet. The scent of jasmine hung in the air from the flowers tied in her hair. She told me how, when she was 18, she was diagnosed with leprosy.

Her family were frightened they would get the disease and kept her in a room at the edge of the village.

"For the first few weeks I kept crying and asking, why me?" she said.

After six months in isolation she was taken away to a clinic and has not seen her family since. The disease robbed the sensation from her right foot - and it became so damaged that eventually it was amputated.

While she was being treated she met her husband - also marked for life by leprosy. More than 130 families live at the colony. They survive on a meagre government pension which many supplement with weaving. But the main occupation is begging.

Many of the disabled who stand outside the temples and at road junctions in Hyderabad carry the marks of leprosy. One man, who'd lost several fingers, told me that he rarely leaves the colony because people are so hostile.

"It's impossible to buy a drink at a cafe," he told me. "People cover their faces, and tell us to leave."

Leprosy may have been officially eliminated as a public health problem in India, but eradication is a different matter.

India has stopped actively searching for leprosy cases - instead relying on communities to recognise the disease. The danger is that patients will either not realise they have the condition or be too scared to come forward.

The Indian government says it is determined to wipe out leprosy, but the signs are that this ancient disease will continue to disfigure and disable well into the 21st Century.

From Our Own Correspondent was broadcast on Saturday, 31 March, 2007 at 1130 BST on BBC Radio 4. Please check the programme schedules for World Service transmission times.